Proposals have already been made in Document AU-A-81304/87 for an undersea telecommunications cable including a conductive metal tube surrounding optical fibers embedded in a material that fills the inside of the tube, electrical insulation surrounding the tube which is made of a conductive metal, and at least one layer of metal wires having high traction strength surrounding the installation and constituting protective armoring. However, such a cable does not provide adequate resistance to the possibility of water infiltrating and propagating longitudinally, particularly in the event of an immersed cable being damaged. Further, the metal wires constituting the protective armoring may be corroded on contact with seawater, e.g. by bacterial action, and this corrosion phenomenon may then give rise to molecular hydrogen being evolved which, under certain conditions, can migrate until it comes into contact with the optical fibers where it gives rise to degraded transmission characteristics. In addition, the conductive metal tube containing the fibers makes the structure expensive for a connection that is not remotely powered, or else it requires a different optical module (i.e. the tube containing the fibers) to be used depending on whether or not the link is remotely powered.
Document EP-A-0 371 660 describes an undersea telecommunications cable having optical fibers in a strength tube, which tube is not used for transporting energy , thereby making it possible to leave the central portion of the cable unaltered regardless of whether the cable is used for remotely powering repeaters or regenerators on a given link. That cable includes a dielectric covering the tube, strength armoring on the dielectric, and an outer protective sheath. Where appropriate, that cable is provided with an internal remote-powering conductive layer constituted by a layer of conductor wires made of copper or aluminum and interposed in the dielectric. The dielectric is then made up from two layers, and the remote-power conductors are sandwiched between these two dielectric layers.
An object of the present invention is to satisfy the same object but with a structure that is more compact and easier to implement, and which is cheaper, which structure also serves to minimize or eliminate electric field concentrations that may cause it to be damaged.